Technical Field
The present disclosure relates to a motor driving controller for driving a motor and a motor driving control method for the motor driving controller.
Background Art
Conventionally, a motor driving controller for driving a brushless motor has been known. For example, JP Unexamined Patent Application Publication. No. 2012-257429 discloses a motor driving controller for driving a brushless motor. In the motor driving controller described in JP Unexamined Patent Application Publication. No. 2012-257429, when a motor is started from a stopped state, the motor is driven to rotate by rectangular wave driving as a first driving system and when a stable rotation is achieved, the driving system is switched from the first driving system to sine wave driving as a second driving system.
The rectangular wave drive has almost no overlapping energization period between coils of respective phases at the time of commutation. Therefore, the rectangular wave driving has characteristics such that a coil current changes drastically thereby causing large vibrations and driving sounds while an output torque is large and step out is unlikely. On the other hand, though there is possibility of step-out, the sine wave driving has a longer overlapping energization period between coils of respective phases at the time of commutation in comparison with the rectangular wave driving, and therefore a coil current changes relatively softly to allow the sine wave driving to have a characteristic such as small vibrations and small driving sounds. Thus, at the time of starting, when the rotor starts to rotate with large fluctuations of the torque and the commutation easily occurs, the following method is adopted. Namely, the driving is effected in accordance with the rectangular wave driving system and, when the steady rotation is about to occur, the system is switched to the sine wave driving system to attenuate the driving sounds at the time of the steady rotation.
However, fan products such as an electric fan, an air cleaner and a ventilating fan are used more frequently under a silent environment such as at night. Therefore, even the noises due to the rectangular wave driving at the time of starting may cause uncomfortableness and the required level of the noise reduction is made far higher. As a result of analyzing the uncomfortableness with this background taken into consideration, the knowledge to the effect that the uncomfortableness increases depending on the sound pressure level of the noises at the time of starting and the duration of the noises at the time of starting has been obtained. Thus, in order to attenuate the uncomfortableness, the way to lower the sound pressure level of the noises at the time of starting by the rectangular wave driving and the method used to shorten the duration of the rectangular wave driving are considered to be effective.
In order to lower the sound pressure level, it is conceivable to enhance the rigidity of components of a motor to suppress the vibration of a motor and to provide a rubber member for absorbing the vibration of a motor. In these cases, the mass of the motor driving controller increases, the cost of the motor driving controller becomes higher and the labor for producing the motor driving controller increases. As described above, the conventional motor driving controller had room for improvement from the viewpoint of restricting the increase in mass and costs as well as attenuating the uncomfortableness of the starting noises. The above-described problem may occur in not only the fan product, but also in a motor for other use.
The present disclosure is related to providing a motor driving controller and a motor driving control method, which can attenuate uncomfortableness due to starting noises by shortening starting time with rectangular wave driving as much as possible in a brushless motor in which a driving waveform is changed.